Two band model

At high temperature, the conductivity was found to increase linearly with temperature and the observed high-temperature MR was positive. In fact, by fitting the data using a simple two-band model] 17] the authors obtained the theoretical curve in Fig. 4 (a). The fitting parameters showed that the ratio Op/ct, where Op and are the partial conductivities of holes and electrons, respectively, decreases with increasing tern-... 

Fig. 4. (a) Magnetic field dependence of the high- and low-temperature MR, respectively. The solid lines are calculated using a simple two-band model for (a) and the 2D weak localization theory for (b) (after Song et o/.[16]). 

Fig. 5. Electrical resistance as a function of the temperature at the indicated magnetic fields for a single microbundle of carbon nanotubes. The solid line is a fit using the two-band model for graphite (see inset) with an overlap A = 3.7 meV and a Fermi level right in the middle of the overlap (after Langer et at. l9 ).

Fig. 19. Hc2(T) of a L11N12B2C single crystal measured parallel 10 the tetragonal c-axis (o). The solid curve was calculated using a two-band model (see text). Dashed lines isotropic single-band (ISB) models with two values...

Fig. 20. (a) Temperature dependence of the upper critical field calculated within a two-band model for several impurity scattering rates yjmp (cm-1). (b) calculated Hc2(0)-vi.-ylmp curve illustrating the transition from the clean to the dirty limit. Dotted line Hc2(0)-y,mp dependence in the dirty limit. (Drechsler et al. 2000 Fuchs... 

Equation 23 goes by the name, Gorter-Nordheim rule it indicates that a plot of e vs. cr( = l/p) will be linear. On the other hand, if one has a single scattering mechanism and two groups of carriers (two bands), then the conductivities rather than resistivities are added a = band model the thermopower is ... 

MODELLING CUPRATE GAPS IN A COMPOSITE TWO-BAND MODEL... 

Pair transfer interaction between the states of an electron system components can cause the gauge symmetry breaking realized in superconductivity. This circumstance forms the basis of the two-band model of superconductivity known already during a considerable time [1,2], The basic advantage of such approaches consists in the possibility to reach pairing by a repulsive interband interaction which operates in a considerable volume of the momentum space. An electronic energy scale is... 

However, meantime the new superconductor MgB2 [36] has been discovered, which shows a clear two-gap behaviour [37], Two-band models have been applied to MgB2 [38-39] and at present this system is addressed as the reigning representative of the two-band superconductivity. 

Modelling Cuprate Gaps in a Composite Two-Band Model... 

Abstract We using our two-band model for the explanation of two coupled... 

Key words Multi-gap, Two-band model, Interband Pairing. 

In this paper, we investigate our two-band model for the explanation the multi-gap superconductivity of MgB2. We apply the model to an electron-phonon mechanism for the traditional BCS method, an electron-electron interaction mechanism for high- Tc superconductivity, and a cooperative mechanism in relation to multi-band superconductivity. 

In this section, we briefly summarize a two-band model for superconductivity. 

In conclusion, we have presented our two-band model with intraband two-particle scattering and interband pairing scattering processes to describing two-gap superconductivity in MgB2. 

Vibronic Renormalization of Superconductivity Gaps in a Two-Band Model of Cuprates... 

To describe the transport through a molecular system having HOMO and LUMO energy levels, one of the applicable models is the Franz two-band model.75-81 This model provides a non-parabolic energy-momentum E(k) dispersion relationship by considering... 

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